Daily bugle rooftop arena:
In versus mode, fight as Spider-Man vs. Venom CPU in the NYC bridge arena. Win to unlock the Daily Bugle Rooftop arena. You may need to complete the game first.

Handsprings:
With Spider-Man, Daredevil, Elektra, or anyone else that does handsprings for a dodging move, hold Y and press Left Analog-stick Away or Left Analog-stick Forward. Keep tapping in that direction and your character will keep doing handsprings.

Unlock all characters and venues easily:
Every ten versus battles unlocks either a venue or a character. The easiest way to do this is on the bridge level, with a second controller. Throw your opponent off the edge of the bridge for an easy victory.